1. Technical Field of the Invention
The present invention relates to a blower for sending air. More particularly, the present invention relates to a blower used for a cooling device which cools an object to be cooled to a temperature not more than a predetermined temperature when a volume of air to be blown out is changed according to a quantity of heat generated by the object to be cooled.
2. Description of the Related Art
A battery cooling device disclosed in the official gazette of JP-A-2004-255960 is provided with a blower for sending air for cooling a battery which supplies electric power to a motor used for running. This blower includes a blowing fan and a drive motor. When the rotating speed of the drive motor is changed, the volume of air blown out from the blowing fan is adjusted, so that a temperature of the battery can be maintained at a temperature not more than a predetermined temperature.
In this connection, in the case of a blower, the rotating speed of the drive motor of which is changed like the drive motor of the battery cooling device disclosed in the official gazette of JP-A-2004-255960, the frequency of the magnetic vibration of the drive motor is changed according to the rotating speed. This magnetic vibration is caused by a periodic change in a magnetic force generated by a stator coil arranged in the drive motor. By this magnetic vibration, the drive motor itself is vibrated. Accordingly, when the frequency of the magnetic vibration is changed, the vibration frequency of the drive motor itself is also changed.
Vibration of the drive motor itself is transmitted to a support member such as a motor support plate, a casing and so forth for supporting and fixing the drive motor. Therefore, when the vibration frequency of the drive motor itself changes and coincides with a resonance frequency of the support member, the support member resonates and a resonance noise is generated.